G-DNA: a twice-folded DNA structure adopted by single-stranded oligo(dG) and its implications for telomeres.
Our dimethyl sulfate modification experiments suggest that (dG)n stretches within single-stranded DNA fragments, which represent the simplest model for telomeric sequences, adopt a complex intrastrand structure other than a simple hairpin. We present a molecular model for the DNA structure that conforms to dimethyl sulfate methylation data. The principal element of this G-DNA structure is a quadruple helix formed by pairwise antiparallel segments of the twice-folded (dG)n stretch. This quadruple core has two wide and two narrow grooves connected by three loop-shaped segments. The strong stacking interactions of the neighboring guanine tetrads and the large number of hydrogen bonds formed can be the primary reasons that such structures are favored over a common hairpin for long (dG)n stretches. Such compact structures may be formed from (dG)n stretches of telomeric sequences.
Panyutin
I G
IG
N. D. Zelinsky Institute of Organic Chemistry, U.S.S.R. Academy of Sciences, Moscow.
Kovalsky
O I
OI
Budowsky
E I
EI
Dickerson
R E
RE
Rikhirev
M E
ME
Lipanov
A A
AA
D002875:Chromosomes / Q000648:ultrastructure; D004247:DNA; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides
D009838:Oligodeoxyribonucleotides; C033538:oligodeoxyguanylic acid; D004247:DNA